A micro wave high-frequency semiconductor element which is formed with a compound semiconductor mainly made of, for example, GaAs or GaN and the like is usually accommodated in a high-frequency semiconductor package and is used. The high-frequency semiconductor package is requested to have an electromagnetic shield function which shields a high-frequency semiconductor element from an external high frequency and an airtight function which protects the high-frequency semiconductor element from, for example, moisture and the like. Further, the high-frequency semiconductor package of this type also is requested to have a heat radiation function of effectively radiating heat produced by the high-frequency semiconductor element.
Conventionally, for a general high-frequency semiconductor package, a package which adopts a structure obtained by combining metal and ceramic and a package made of ceramic are well known. Further, as introduced in, for example, JP 3606837 B1, a package obtained by resin-molding a semiconductor element is well known. Furthermore, as introduced in JP 2008-42063 A, a package which makes a device to increase heat radiation characteristics is invented.
However, a semiconductor package obtained by resin-molding a high-frequency semiconductor element as introduced in JP 3606837 B1 has many problems in terms of poor electromagnetic shield performance, or electric characteristics of resin or permeability with respect to, for example, moisture and the like, and therefore performance and reliability of the high-frequency semiconductor element are hardly guaranteed.
By contrast with this, a semiconductor package which adopts a structure obtained by combining metal and ceramic is made of ceramic, and therefore is expensive. Further, this semiconductor package is formed in many cases by way of secondary adhesion of a heat spreader which is made of a metal and is a radiator using, for example, silver solder, and therefore there is a problem with adhesion position precision of the heat spreader which is made of a metal and there is a problem that manufacturing cost becomes high due to this process.
Furthermore, to secure heat radiation characteristics in a semiconductor package made of ceramic or resin by letting heat out from a lower surface of a semiconductor element to an outside of the semiconductor package, it is necessary to provide through-holes or via holes highly densely in ceramic or resin. When desired heat radiation characteristics are not satisfied only by providing through-holes or via holes highly densely, it is necessary to make a device of, for example, adopting a structure in which a heat radiation electrode is attached to a top surface of a semiconductor element as introduced in JP 2008-42063 A to further improve the heat radiation characteristic. However, this device does not satisfy a sufficient heat radiation property. This semiconductor package made of ceramic or resin has a limited amount of heat generation of a semiconductor element which can be mounted.